I think you need to ensure you have a neutral area like a puppy pen or dog crate, fill it with hay but no litter tray or anything that they can become possessive over. Scatter food and treats in the hay for foraging, plenty of water in a bowl and bottles, throw in wet herbs like dill or chopped spring greens as a distraction or dandelions, it also keeps them eating together.
Your looking for calm gentle approaching and then if anything a bit of chasing and or mounting, if it gets nasty with circling or locking on biting, gently separate them, if one is locked on use a water spray on the biter to get them to release their grip - seems brutal but they will then be distracted by cleaning themselves off.
There are lots of threads regarding bonding and some propose what I think are very brutal stressful methods like putting them in a cardboard box on a washing machine-it's completely unnecessary I think - you want your rabbits to be relaxed and become friends not start the process with fear and confusion as it will only make an artifical bond anyway that later on could break, I've found housing rabbits side by side really helps them get used to each others smells and movements/habits before bonding, after a short time they are used to seeing one another and will flop out next to each other etc and watch each other. You can also swap scented items like their toys/litter trays so they become familiar with the scent of each other prior to bonding.
Another thing I don't agree with is prolonged confinement in bonding, I think if it's working out well and the rabbits are getting along with mutual grooming, eating together, minimal humping and generally seem relaxed then that's good enough to extend the space, it's entirely your judgement how much by and it's essential that they are housed in neutral territory - not put in the accomodation that one was more familiar with than the other, so thoroughly disenfecting/adapting in some way to make it slightly different is a good idea.
Have a good read through all the threads and pick out the key bits which will apply to your rabbits, there are no hard and fast rules and no real 'experts' as such because all rabbits and all pairings/bondings are different really because the animals and the people doing it are, best of luck, stay calm and be gentle :wave: